Manually operated travelling vehicle with auxiliary power

ABSTRACT

A manually operated travelling vehicle with an auxiliary power device, which can detect a rotating torque applied to a rotating crank shaft ( 40 ) in non-contact manner. Supported on a body ( 15 ) is a manually operated prime mover wheel ( 5 ). A rotating coil ( 201 ) is provided coaxially on the prime mover wheel ( 5 ). A variable impedance device ( 202 ) is electrically connected to the rotating coil ( 201 ) such that impedance changes depending upon a load applied to the prime mover wheel ( 5 ). A stationary coil ( 101 ) is fixed to the body ( 15 ) to be coaxial with and spaced from the rotating coil ( 201 ) with a predetermined interval therebetween and is electromagnetically connected to the rotating coil ( 201 ). A detection circuit ( 109 ) is connected to the stationary coil ( 101 ) to detect a change in current or voltage applied to the stationary coil ( 101 ) from the rotating coil ( 201 ) in accordance with an impedance change in the variable impedance device ( 202 ). A control unit ( 130 ) controls a power source for the auxiliary power device on the basis of an output value issued from the detection circuit ( 109 ).

TECHNICAL FIELD

The present invention relates to manpowered vehicles such as bicyclesthat are provided with auxiliary power apparatuses for supplementingmanpower in accordance with the load on the manpower.

BACKGROUND ART

A known auxiliary powered bicycle has a drive wheel to which a motor isconnected. When the bicycle is driven by manpower, the motor is drivenin accordance with the load applied to the pedal. This producesauxiliary power that supplements the manpower. Thus, the bicycle can bedriven with a low degree of manpower.

Japanese Unexamined Patent Publication No. 4-100790 describes an exampleof how to measure the drive force applied by man. A torsion bar is usedas a pedal crank axle. A detector such as a potentiometer or a straingauge is arranged on the torsion bar to detect the twisted amount of thetorsion bar and thus measure the applied torque.

However, the potentiometer or the strain gauge is arranged on a rotatedaxle. Thus, signals representing the detected value must be output usinga slip ring or a brush. As a result, there is a tendency for noise to beincluded in the signals due to friction and abrasion. This makes itdifficult to detect torque accurately.

In addition, the employment of a slip ring or a brush produces auralnoise caused by friction as the bicycle moves. Such noise may make therider feel uncomfortable.

Furthermore, the slip ring and the brush must be replaced when abrasionoccurrs. Such replacement is burdensome.

Accordingly, it is an objective of the present invention to provide anauxiliary powered manpowered vehicle having a torque detector thatdetects the torque applied to a rotated crank axle in a non-contactmanner in order to prevent the production of noise caused by friction orabrasion and detect torque accurately.

It is a another objective of the present invention to provide anauxiliary powered manpowered vehicle that prevents the production ofaural noise due to friction when the bicycle travels and thus does notmake the rider feel uncomfortable.

It is also an objective of the present invention to provide an auxiliarypowered manpowered vehicle that prevents abrasion between parts and thuseliminates the necessity for the replacement of such parts.

It is a further objective of the present invention to provide anauxiliary powered manpowered vehicle that detects a load acting alongthe rotating direction of a crank axle and a drive gear within the sameplane and thus uses restricted space in an effective manner.

DISCLOSURE OF THE INVENTION

The auxiliary powered manpowered vehicle according to the presentinvention is a man powered vehicle, which includes an auxiliary powerapparatus having a power source for supplementing the driving of themanpowered vehicle. The manpowered vehicle includes a main body, arotated body supported by the main body and driven by manpower, a rotarycoil arranged coaxially with the rotated body, a variable impedancedevice electrically connected to the rotary coil and having impedancevaried in accordance with the load applied to the rotated body, a fixedcoil fixed to the main body such that the fixed coil is concentric withand spaced by a predetermined distance from the rotary coil and iselectromagnetically coupled with the rotary coil, a detecting circuitconnected with the fixed coil and detecting changes in electric currentor voltage of the fixed coil caused by the rotary coil in accordancewith the impedance varied by the variable impedance device, and acontroller for controlling the power source based on the output value ofthe detecting circuit.

In such structure, the application of load to the rotated body variesthe impedance of the variable impedance device, which is arranged in therotary coil. The varied impedance is transmitted to the fixed coil byelectromagnetic coupling between the rotary coil and the fixed coil.This varies the electric current or the voltage of the fixed coil. Thechange in the electric current or voltage is detected by a detectingdevice. The power source of the auxiliary power device is driven inaccordance with the detected value.

In the present invention, the load applied to the rotated body variesthe impedance of the variable impedance device, which rotates integrallywith the rotated body. The variation is transmitted to the detectingcircuit by way of the electromagnetic coupling between the rotary coiland the fixed coil. Therefore, a slip ring is not necessary forextracting torque signals and the production of noise resulting fromfriction or abrasion is prevented. Accordingly, the torque applied tothe rotated body is measured accurately. Furthermore, noise produced byfriction during the movement of the vehicle is eliminated. Thus, theoperator does not feel discomfort that would result from such frictionnoise. Additionally, there is no abrasion of parts. Therefore,replacement of parts is not necessary. This enhances reliability anddurability.

The manpowered vehicle according to the present invention furtherprovides a support plate movable along the axial direction of therotated body with the fixed coil being arranged on the support plate, aspacer arranged between the support plate and the rotated body tomaintain the distance between the two coils, and an urging member foraffecting the support plate such that the spacer maintains the distance.With this structure, the distance between the fixed coil and the rotarycoil is maintained by the spacer. Accordingly, the distance between thefixed coil and the rotary coil is maintained even when swaying orvibrating occurs. This improves the reliability and accuracy of themeasured torque signal.

It is preferable that the spacer includes a ball bearing having a pairof races, and a plurality of balls held between the races. With thisstructure, the fixed coil and the rotary coil are rotated relatively bythe ball bearing.

The expansion and contraction of the urging member and the existence ofthe spacer maintains a constant distance between the fixed coil and therotary coil even if the length of the axle projecting from the main bodydiffers due to application to a vehicle having dimensional differencesresulting from production or application to a different type of vehicle.Thus, the two coils may be designed to have a constant distancetherebetween for each vehicle type. In addition, fine adjustment of thedistance between the coils is not necessary.

The arrangement of the ball bearing between the support plate, on whichthe fixed coil is located, and the rotated body, on which the rotarycoil is located, maintains smooth rotation even if the urging memberurges the support plate toward the rotated body.

It is preferable that the auxiliary power apparatus includes a powersource circuit for supplying electric power in a cyclic manner to thefixed coil. In this case, the cyclic electric power supplied to thefixed coil by the power source circuit and electromagnetic inductionbetween the fixed coil and the rotary coil generates inducedelectromotive force in the rotary coil. Furthermore, mutual inductionaffected by impedance, which is varied by the variable impedance device,acts on the fixed coil.

In an embodiment according to the present invention, the rotated bodyincludes a crank axle pivotally supported by the main body and a drivegear rotatably coupled to the periphery of the crank axle. A crank armhas a basal end fixed to the crank axle and a distal end on which apedal is arranged to rotate the crank arm integrally with the crankaxle. The drive gear is connected to a manpowered drive wheel. The crankaxle and the drive gear are connected by an elastic body to rotateintegrally with each other. With this structure, rotation of the pedalis transmitted to the drive gear by way of the elastic body, and theload acting on the drive wheel relatively displaces the positionalrelationship between the crank axle and the drive gear in the rotatingdirection against the elasticity of the elastic body.

In this case, the drive gear does not move in the axial direction of thecrank axle. This eliminates the need for space in the axial directionand thus enables the torque detector to have a thin structure.

Additionally, the variable impedance device includes an element forvarying the impedance in accordance with the amount of relativedisplacement between the crank axle and the drive gear.

The variable impedance device preferably includes a core made of amagnetostrictive material and a coil arranged on one part of an outersurface of the core. The remaining part of the outer surface of the coreis supported between the crank axle and the drive gear. With thisstructure, the impedance of the coil is varied by deformation of thecore that corresponds to the load acting on the drive gear.

In a further embodiment, the crank arm, which is fixed to the crankaxle, includes a pressing piece that projects toward the drive gear, andthe drive gear includes a receiving piece facing the pressing piecealong the direction of rotation. The core is arranged between thepressing piece and the receiving piece. In such a structure, the core isarranged in the space formed between the crank arm and the drive gear.In this case, the arrangement of the core between the crank arm and thedrive gear eliminates the need of a separate space for the accommodationof the core. Furthermore, the core is surrounded by the drive gear andthe crank arm and thus protected. This prevents the core from beingdamaged.

It is preferable that a container accommodate the core and the coil, andthat the container be made of a magnetic body. In such a structure, thecontainer forms a magnetic circuit about the coil and thus eliminatesleakage flux from portions encompassed by the container. Preferably, thecontainer has a cup-like shape.

It is preferable that a pressing surface of the pressing piece or areceiving surface of the receiving piece is connected to the core by anelastic plate. In such a structure, the pressing surface of the pressingpiece or the receiving surface of the receiving piece may be inclinedwith respect to the end surface of the core.

Either the pressing surface of the pressing piece or the receivingsurface of the receiving piece may be round, and a plate member and anelastic plate may be used to connect the round surface to one endsurface of the core. In such structure, the round pressing surface ofeither the pressing piece or the receiving piece abuts the plate memberat a single point. This applies force on the end surface of the core ina uniform manner by means of the elastic member. More specifically, theplate member employs a magnetic body. This forms a magnetic circuit,together with the container, about the coil. Thus, in addition to theportions encompassed by the container, leakage flux is eliminated fromthe portions encompassed by the plate member.

The detecting circuit employed in the present invention measures theelectric current flowing through the fixed coil or the coil voltage. Ina preferred embodiment, the auxiliary power apparatus includes anoscillator circuit that varies the oscillating frequency in accordancewith the impedance varied by the variable impedance device. With thisstructure, variation of the impedance of the variable impedance devicevaries the inductance of the fixed coil entirely. This varies theoscillating frequency of the oscillator circuit. In this case, thevarious circuits of the rotary coil need not be supplied with electricpower. This simplifies the circuit structure.

In a further embodiment, the auxiliary power apparatus includes anoscillator circuit that varies the oscillating frequency based on theimpedance varied by the variable impedance device. The oscillatorcircuit is connected to the rotary coil. With this structure, variationof the impedance of the variable impedance device varies the oscillatingfrequency of the oscillator circuit. The varied oscillating frequency istransmitted to the circuit of the fixed coil by electromagnetic couplingbetween the rotary coil and the fixed coil. In this case, the rotarycoil circuit is actuated using the induced electromotive force generatedby the rotary coil as an electric power source.

In another embodiment of the present invention, changes in the torqueapplied to the crank axle are detected based on fluctuations of theoscillating frequency. Mechanical differences related to theinstallation of the rotary coil are irrelevant to changes in the torque.Accordingly, torque is detected with high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing the entire structure of an auxiliarypowered manpowered vehicle according to a first embodiment of thepresent invention;

FIG. 2 is a rear left perspective view of the auxiliary poweredmanpowered vehicle of FIG. 1;

FIG. 3 is a plan view showing a driving mechanism of the auxiliarypowered manpowered vehicle of FIG. 1;

FIG. 4 is an exploded perspective view showing the structure of apedalling mechanism employed in the first embodiment;

FIG. 5 is a cross-sectional view taken along line 5—5 in FIG. 4 andshowing the pedalling mechanism;

FIG. 6 is a front view of the pedalling mechanism of FIG. 4.

FIG. 7 is a block diagram showing a torque detecting circuit employed inthe first embodiment;

FIGS. 8(a) and 8(b) are graphs showing the waveform of the voltageapplied to a fixed coil and the waveform of the current produced by thevoltage application;

FIG. 9 is a graph showing the relationship between the torque applied toa drive gear and the output of a differential amplifier;

FIG. 10 is a front view showing the structure of a pedalling mechanismemployed in a second embodiment of the present invention;

FIG. 11 is a block diagram showing a torque detecting circuit employedin the second embodiment;

FIG. 12 is a block diagram showing a frequency monitoring circuitemployed in the second embodiment;

FIGS. 13(a) and (b) are graphs plotted when using the torque detectingmethod of the second embodiment and show (a) the waveform of the voltageapplied to a fixed coil and (b) the waveform of the voltage produced bya bandpass filter;

FIGS. 14(a) and (b) are graphs plotted when using another torquedetecting method of the second embodiment and show (a) the waveform ofthe voltage applied to a fixed coil and (b) the waveform of the voltageproduced by a bandpass filter;

FIG. 15 is a block diagram showing a torque detecting circuit employedin a third embodiment;

FIG. 16 is a graph showing the characteristics of a core and a coil,which are employed in the second to a seventh embodiment;

FIG. 17 is a block diagram showing a torque detecting circuit employedin a fourth embodiment;

FIG. 18 is a front view showing the structure of a drive gear and acrank arm employed in a fifth embodiment and a sixth embodiment;

FIG. 19 is an enlarged cross-sectional view taken along line 19—19 inFIG. 18 showing the fifth embodiment;

FIG. 20 is an enlarged cross-sectional view corresponding to FIG. 19showing the sixth embodiment;

FIG. 21 is a cross-sectional view of a pedal structure employed in theseventh embodiment; and

FIG. 22 is a cross-sectional view showing another pedal structure thatmay be employed in the seventh embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments according to the present invention will now be describedwith reference to the drawings.

The present invention is embodied in a two-wheel bicycle having a rearwheel 17, which serves as a drive wheel. When turning pedals 62, thedirection in which the bicycle 1 advances is referred to as frontward,the direction in which rotating parts rotates is referred to as forward,and the leftward and rightward directions are determined with respect tothe advancing direction of the bicycle 1.

The entire structure of the bicycle 1 will first be described.Afterward, first to fourth embodiments, which are related to a torquedetector 50, fifth and sixth embodiments, which are related to theinstallation of a core 90, and a seventh embodiment, which is related tothe installation of a rotary coil 201 and a fixed coil 101, will bedescribed.

As shown in FIG. 1, the bicycle 1 has a front wheel 16 located at afront portion of a frame 11. The rear wheel 17, which serves as thedrive wheel, is located at the rear portion of the frame 11.

A seat tube 12 is located at the middle portion of the frame 11. Asaddle 13 is mounted on a top end of the seat tube 12. A bottom bracket15 is provided at a bottom end of the seat tube 12 to pivotally supporta pedalling mechanism 4, as shown in FIG. 2.

As shown in FIGS. 4 and 5, the pedalling mechanism 4 includes a crankaxle 40 pivotally supported in the bottom bracket 15, a crank arm 61fixed on each end of the crank axle 40, a pedal 62 pivotally supportedat the distal end of each crank arm 61, and a drive gear 5. The drivegear 5 is a sprocket and fitted to the right end of the crank axle 40and supported rotatably relative to the crank axle 40.

More specifically, a block 41 projects from each end of the crank axle40 (only right end shown) to engage the associated crank arm 61. Theblock 41 is received in a square cavity 63 formed at the basal end ofthe crank arm 61. A nut 77 is inserted through a washer 76 and fastenedto a threaded hole, which is formed in the block 41, to fix the crankarm 61 to the crank axle 40.

The crank axle 40 is connected to the drive gear 5 by coil springs 55.The rear wheel 17 has an axle 72. A driven gear 73, which is a sprocket,is fit on the axle 72. An endless chain 75 connects the driven gear 73and the drive gear 5 to transmit drive force produced by manpower to therear wheel 17. A known one-way clutch (not shown) is arranged betweenthe axle 72 of the rear wheel 17 and the driven gear 73.

As shown in FIG. 6, the drive gear 5 has a toothed portion 51 defined atits periphery, a hub ring 54 defined at the central portion, and fiveribs 52 connecting the toothed portion 51 and hub ring 54. A rotatedcircuit 200 is arranged on the surface of the drive gear 5 that is closeto the bottom bracket 15.

The outer diameter of the rear wheel 17 is smaller than that of thefront wheel 16. An auxiliary power unit 2 is installed on the frame 11between the seat tube 12 and the rear wheel 17 to supplement the driveforce produced by manpower. The auxiliary power unit 2 includes a motor22, which serves as an auxiliary power source, and a transmittingmechanism 3, which decelerates the speed of the motor 22 and transmitsthe rotating force of the motor 22 to the rear wheel 17.

More specifically, as shown in FIGS. 2 and 3, a base plate 24 is securedto the frame 11 by a fastener 21. A fixed circuit 100, which includes afixed coil 201 that will be described later, is arranged on the uppersurface of the base plate 24.

The base plate 24 has a wall, the right side on which the motor 22 isarranged. The motor 22 has an output shaft 23, which is fixed to a drivepulley 31. The output shaft 23, the drive pulley 31, and a first drivenpulley 33 are supported at the left side of the wall of the base plate24. A belt 32 connects the drive pulley 31 and the first driven pulley33.

A second driven pulley 35, which is co-axial with the first drivenpulley 33 and has a diameter that is smaller than that of the firstdriven pulley 35, is fixed to one side of the first driven pulley 33.

The rear wheel 17 has a rim 71. A third driven pulley 37 is formedintegrally with the left side of the rim 71. A belt 36 connects thesecond driven pulley 35 and the third driven pulley 37.

The rotating force of the motor 22 is transmitted to the first drivenpulley 33 from the drive pulley 31, which rotates integrally with theoutput shaft 23 of the motor 22, by the belt 32. The rotating force isfurther transmitted from the second driven pulley 35 to the third drivenpulley 37 by the belt 36. Thus, the speed of the motor 22 can bedecelerated when driving the rear wheel 17 with the transmittingmechanism 3. The power produced by the motor 22 is controlled by acontroller 130 based on torque detecting signals sent from the torquedetector 50.

A battery 26, which serves as the electric power source of the motor 22,is attached to the seat tube 12.

The structure of the torque detector 50 will now be described.

FIRST EMBODIMENT

In a first embodiment, the coil springs 55 are arranged between thecrank axle 40 and the drive gear 5. The rotation of the crank axle 40 istransmitted to the drive gear 5 by the coil springs 55. The torqueapplied to the drive gear 5 is measured by detecting the relativedisplacement amount between the crank axle 40 and the drive gear 5 inthe rotating direction when the coil springs 55 contract.

As shown in FIG. 4, a disk-like support plate 66 is secured to the basalend of the right crank arm 61. Five equally spaced pressing pieces 68extend from the periphery of the support plate 66 on the surface facingthe drive gear 5 (left surface).

As shown in FIG. 6, a holding piece 58 is secured to each of the fourribs 52 of the drive gear 5 to hold one of the coil springs 55, whichserves as an elastic body and which extends in the reverse rotatingdirection of the drive gear 5. One of the holding pieces 58 is alsosecured to the remaining rib 52 to hold a direct-acting typepotentiometer 202, which serves as a variable impedance means and whichextends in the reverse rotating direction of the drive gear 5. Thepotentiometer 202 includes a detecting pin 203 to detect displacement.The projecting amount of the pin 203 varies an electric resistance valuein a proportional or inverse proportional manner.

The distal end of the coil springs 55 abuts against four of the pressingpieces 68, while the distal end of the detecting pin 203 of thepotentiometer 202 presses one of the pressing pieces 68.

In this structure, if the pedals 62 are turned, the support plate 66rotates integrally with the crank axle 40. This causes the four pressingpieces 68, which oppose the coil springs 55, to press the coil springs55 and rotate the drive gear 5, which further rotates the rear wheel 17with the chain 75. If the force applied to the drive gear 5 when turningthe pedals 62 is small and the load applied to the rear wheel 17 is thussmall, that is, if the bicycle advances easily, the contracted amount ofthe coil springs 55 is small. Hence, the crank axle 40 and the drivegear 5 substantially rotate integrally with each other withsubstantially no relative rotational displacement. Accordingly, thedetecting pin 203 of the potentiometer 202 is substantially not pressedby the associated pressing piece 68.

On the other hand, if the force applied to the drive gear 5 is large andthe load acting on the rear wheel 17 is thus large, that is, if it isdifficult for the bicycle 1 to advance, the coil springs 55 pressed bythe pressing pieces 68 deform greatly. This causes rotationaldisplacement of the drive gear 5 with respect to the crank axle 40. Inthis state, the detection pin 203 of the potentiometer 202 is pressed bythe associated pressing piece 68 such that its projecting amount changesgreatly and thus varies the resistance value.

As shown in FIG. 5, a cross-sectionally U-shaped ring core 43, which hasan opening that faces the bottom bracket 15, is arranged in the side ofthe hub ring 54 facing the bottom bracket 15. A rotary coil 201, whichis wound to extend in the rotating direction of the drive gear 5, isarranged in the ring core 43. As shown in FIG. 7, the rotary coil 201 iselectrically connected to the potentiometer 202 to form the rotatedcircuit 200.

At a position corresponding to the rotary coil 201 in the bottom bracket15, a cross-sectionally U-shaped ring core 42 having an opening thatfaces the rotary coil 201 is arranged. The fixed coil 101, which iswound to extend in the rotating direction of the drive gear 5, isarranged in the ring core 42 parallel to and in the vicinity of therotary coil 201. A closed magnetic circuit is formed by arranging thecross-sectionally U-shaped ring cores 42, 43 with their openings facingeach other. The ratio of the number of windings of the coils 101, 201 isarbitrary and may be, for example, 1 to 1. However, the ratio varies inaccordance with the conditions of the element, or the like, that isemployed as the variable impedance means.

As shown in FIG. 7, the fixed coil 101 has a first end connected to adirect current power source 103 of an electric power source circuit 102,which includes a switching transistor 105, to form the fixed circuit100. Although the space between the coils 101, 201 is preferably onemillimeter or smaller, the space is not limited to such values.

The fixed coil 101 also has a second end which is grounded by way of aresistor 106. The collector side of the transistor 105 is grounded byway of a circulating diode 104.

A differential amplifier 109, which serves as a detecting means, has aninput connected to the fixed coil 101 and the resistor 106 and outputsthe voltage difference between the voltage drop in the current flowingthrough the fixed coil 101 caused by the resistor 106, and a referencevoltage V_(ref), which will be described later. The voltage differenceis smoothed by a low-pass filter 108 and then supplied to the controller130.

A driver circuit 107 inputs a rectangular wave signal having apredetermined interval (about 20 kHz), as shown in FIG. 8(a), into thebase of the transistor 105. The ON/OFF of the signal controls the supplyof electric power and applies a rectangular wave voltage to the fixedcoil 101.

Therefore, a pulsating current flows through the fixed coil 101. Mutualinduction of the fixed coil 101 and the rotary coil 201 causes thecurrent flowing through the fixed coil 101 to be affected by changes inthe impedance of the rotated circuit 200, which includes the rotary coil201. The coils 101, 201 are not connected directly. Thus, inducedelectromotive force is generated in the rotary coil 201 by the mutualinduction that occurs between the rotary coil 201 and the fixed coil101. Current then flows in the rotated circuit 200 and generates selfinduction electromotive force in the rotary coil 201. Accordingly,induced voltage corresponding to the electromotive force, which is thesum of the mutual induction electromotive force and the self inductionelectromotive force, is generated. The induced voltage generates currentthat flows through the rotated circuit 200. The current causes mutualinduction acting on the fixed coil 101 and generates inducedelectromotive force in the fixed coil 101.

If the pedals 62 are not turned or if the pedals 62 are turned but thedrive gear 5 rotates integrally with the crank axle 40, there is norelative displacement between the drive gear 5 and the crank axle 40 inthe rotating direction. Thus, the resistance value of the potentiometer202, which is connected to the rotary coil 201, remains substantiallyunchanged. The rotary coil 201 and the fixed coil 101 are coaxial.Hence, interlinkage magnetic flux does not change even if the rotarycoil 201 is rotated with respect to the fixed coil 101 since the rotarycoil 201 and the fixed coil 101 are concentric. In this state, thecurrent that flows through the fixed coil 101 has a predeterminedwaveform corresponding to the voltage generated by the self inductionand mutual induction of the fixed coil 101, as shown by the solid linein FIG. 8(b).

If there is no relative displacement between the drive gear 5 and thecrank axle 40, part of the ON/OFF control signals applied to the base ofthe transistor 105 by the driver circuit 107 is output as the referencevoltage waveform V_(ref) through an integrating circuit and applied to areference voltage terminal of the differential amplifier 109 such thatthe voltage waveform at the resistor 106 matches the waveform and thephase of the reference voltage waveform V_(ref) .

A great load is applied to the drive gear 5 when turning the pedals 62to start moving the bicycle 1, accelerate the bicycle 1, or climb slopeswith the bicycle 1. The load compresses and deforms the coil spring 55.This displaces the drive gear 5 with respect to the crank axle 40.

If a displacement takes place between the drive gear 5 and the crankaxle 40, the detecting pin 203 of the potentiometer 202 is pressed bythe associated pressing piece 68. This increases the resistance valueand varies the current flowing through the rotated circuit 200.Accordingly, the current flowing through the fixed coil 101 is affectedby the change in the resistance value such that, as shown in FIG. 8(b),the waveform changes from the predetermined waveform (solid line) to,for example, the waveform shown by the dashed line.

The voltage waveform measured at the resistor 106 as caused by thecurrent waveform is proportional to the waveform change. Thedifferential amplifier 109 measures the difference between the detectedvoltage waveform and the reference voltage waveform V_(ref) to output avoltage difference signal.

The voltage difference signal detected by the differential amplifier 109is smoothed by the low-pass filter and sent to the controller 130 as adirect current voltage signal.

The controller 130 includes a memory (not shown) in which therelationship between the voltage difference and the torque applied tothe drive gear 5, as shown in FIG. 9, is saved. The motor 22 generates adrive force corresponding to the voltage difference signal. The driveforce is transmitted to the rear wheel 17 by the transmitting mechanism3 to supplement manpower.

In this first embodiment, signals are transmitted between the rotarycoil 201 and the fixed coil 101 via a predetermined space therebetween.This prevents the generation of noise that would be generated whenemploying a slip ring or a brush. Thus, torque is detected accurately.Furthermore, the production of uncomfortable aural noise caused byfriction, which would be generated when using a slip ring or a brush, isprevented. Additionally, there are no worn parts to replace.

In this embodiment, the drive gear 5 and the crank axle 40 are connectedby the coil springs 55 such that they are rotated integrally with eachother. Thus, if a load is applied, the drive gear 5 and the crank axle40 are displaced relative to each other in the rotating direction.However, the drive gear 5 and the crank axle 40 are not moved axially.Accordingly, space for permitting such movement of the drive gear 5 neednot be provided. Thus, the torque detector 50 may have a thin structure.

In this embodiment, the rotary coil 201 is arranged in the drive gear 5.However, the rotary coil 201 may be arranged in the peripheral portionof the crank axle 40.

In this embodiment, the direct-acting type potentiometer 202 is employedas the variable impedance means. However, a rotating type potentiometer,other types of variable resistors (e.g., magnetic resistance device andmagnet), a variable capacitance capacitor, or a variable impedance coilmay also be employed as the variable impedance means.

In this embodiment, the coil springs 55 are employed as the elasticbody. However, leaf springs, rubber, or the like may also be employed asthe elastic body.

SECOND EMBODIMENT

In the first embodiment, the torque applied to the drive gear 5 ismeasured by detecting the change in voltage at the resistor 106 whencurrent flows through the fixed coil 101.

As shown in FIGS. 10 to 13, the second embodiment employs an inductor asa variable impedance means. An LC oscillator circuit 207 is provided inthe rotated circuit 200 to serve as a rotated oscillating means. Theoscillating frequency of the LC oscillator circuit 207 is varied inaccordance with the torque applied to the drive gear 5. The signalcomponent of the LC oscillator circuit 207 is then superimposed with thevoltage waveform of the rotated circuit 200 and transmitted to the fixedcoil 101 via electromagnetic induction. The oscillating frequency of theLC oscillator circuit 207 is measured by the fixed circuit 100 to detectthe torque applied to the drive gear 5. The description of thisembodiment will center mainly on parts differing from the firstembodiment.

As shown in FIG. 10, a support plate 166 is fixed to the basal end ofthe crank arm 61. A pressing piece 168 extends from the peripheralportion of the support plate 166. The drive gear 5 has five ribs 52, oneof which has a receiving piece 158 extending therefrom and arrangedfacing the pressing piece 168. A rotated circuit 200, which isillustrated in FIG. 11, extends between the rib 52 having the receivingpiece 158 and the adjacent rib 52.

The pressing piece 168 and the receiving piece 158 are connected to eachother by a cylindrical core 90, which is made of a magnetostrictivematerial. Thus, the crank axle 40 and the drive gear 5 are rotatedintegrally with each other.

A coil 91 is wound about the core 90 to form an inductor, which servesas the variable impedance means. The coil 91 is connected to the rotatedcircuit 200.

The rotated circuit 200 has a rotary coil 201, which is arranged in thevicinity of the fixed coil 101, and a rectifying power source circuit204. The rectifying power source circuit 204 is connected to the LCoscillator circuit 207, which oscillates sine waves, the core 90 andcoil 91, which serve as an inductance circuit of the LC oscillatorcircuit 207, and an amplifier 208, which amplifies the signalsoscillated by the LC oscillator circuit 207 and transmits the signals tothe rotary coil 201.

The rectifying power source circuit 204 includes a rectifying/smoothingcircuit 205 and a voltage stabilizing circuit 206. The electromotiveforce generated in the rotary coil 201 by electromagnetic induction,which is based on the alternating voltage of the fixed coil 101, isrectified and smoothed by the rectifying/smoothing circuit 205. Thevoltage stabilizing circuit 206 then stabilizes the voltage of theelectromotive force and actuates the rotated circuit 200.

As shown in FIG. 11, the fixed circuit 100 includes the power sourcecircuit 102, the fixed coil 101, which is connected to the power sourcecircuit 102, and a bandpass filter 111, through which signals having thesame frequency bandwidth as the LC oscillator circuit 207 pass. Thefixed circuit 100 includes a frequency measuring circuit 120 connectedto the amplifier 112, and a controller 130, which is connected to thefrequency measuring circuit 120. In the same manner as the firstembodiment, the fixed circuit 100 is arranged on the base plate 24.

The power source circuit 102 includes a direct current power source 103,which generates a direct current voltage using the battery 26 fordriving the motor 22, and a switching circuit 110, which ON/OFF drivesthe voltage generated by the direct current power source 103 at apredetermined interval (about 20 kHz) by means of pulse width modulation(PWM). This causes a rectangular waveform voltage having a predeterminedinterval to be applied to the fixed coil 101.

As shown in FIG. 12, the frequency measuring circuit 120 has acomparator 121, an edge detecting circuit 122, and a counter circuit123. The voltage waveform (oscillating waveform) transmitted from therotated circuit 200 passes through the bandpass filter 111 to separatethe switching waveform of the power source circuit 102. The amplifier112 then amplifies the waveform. Afterward, the comparator circuit 121compares the amplified waveform with a predetermined voltage. Theportions of the voltage waveforms that are equal to or greater than thepredetermined voltage are converted to the power source voltage level(high level). The remaining portions are converted to the ground levelto synthesize a square wave. The edge detecting circuit 122 detects theleading edge and trailing edge of the square wave to form edge pulses.Thus, edge pulses, which have a cycle corresponding to the frequency ofthe alternating voltage waveform transmitted to the fixed coil 101, areobtained.

The edge pulses are input to the counter circuit 123, which operates ata speed much faster than the oscillating frequency of the LC oscillatorcircuit 207, for example, a free-running frequency of 8 MHz. Each timethe edge pulses are input to the counter circuit 123, the counter valueis output to the control circuit 130 and then cleared. As a result, thecyclic interval of the edge pulses is represented as the counter valueof the counter circuit 123. Accordingly, the frequency of the voltagewaveform transmitted to the fixed coil 101 from the rotated circuit 200,or the oscillating frequency of the LC oscillator circuit 207, isdetected.

The operation of the fixed circuit 100 and the rotated circuit 200employed in this embodiment will now be described with reference toFIGS. 11 and 12.

When the power source circuit 102 of the fixed circuit 100 applies arectangular waveform voltage (20 kHz), which is ON/OFF controlled by theswitching circuit 110, on the fixed coil 201, electromagnetic inductionbetween the rotary coil 201 and the fixed coil 101 generates an inducedelectromotive force in the rotary coil 201 in the same manner as thefirst embodiment. Thus, an induced current flows in the rotated circuit200.

The electromotive force generated in the rotated circuit 200 forms analternating waveform. The rectifying power source circuit 204 rectifiesand smooths the alternating waveform to obtain a constant voltage. Therectifying power source circuit 204 supplies the LC oscillator circuit207 with the constant voltage so that it oscillates at a frequencycorresponding to the inductance of the coil 91 (20 kHz or higher and 100kHz or lower).

The oscillating voltage waveform generated by the LC oscillator circuit207 is amplified by the amplifier 208 and applied to the rotary coil201. The voltage waveform is superimposed with the voltage waveform ofthe rotated circuit 200 causing mutual induction between the rotary coil201 and the fixed coil 101, which generates an induced electromotiveforce in the fixed coil 101. In other words, as shown in FIG. 13(a), thevoltage waveform generated by mutual induction, which occurs due to therectangular waveform voltage supplied by the power source circuit 102,is superimposed with the oscillating voltage waveform oscillated by theLC oscillator circuit 207.

As shown in FIG. 13(b), the bandpass filter 111 extracts frequencycomponents from the signal generated by the LC oscillator circuit 207 onthe voltage waveform of the fixed coil 101 and inputs the filteredwaveform to the frequency measuring circuit 120 by way of the amplifier112.

The frequency measuring circuit 120 counts the cycles of the edge pulsesproduced by the input voltage waveform. The count value is then input tothe control circuit 130. The count value indicates the torque applied tothe drive gear 5.

The controller circuit 130 includes a memory (not shown) to store therelationship between the torque to be applied to the drive gear 5 andthe output value of the frequency measuring circuit 120.

A great load is applied to the drive gear 5 when turning the pedals 62to start moving the bicycle 1, accelerate the bicycle 1, or climb slopeswith the bicycle 1. The load compresses and deforms the coil spring 55,which displaces the drive gear 5 with respect to the crank axle 40. Theload applies a compressing force on the core 90, which is made of amagnetostrictive material and arranged between the crank axle 40 and thedrive gear 5. This alters the magnetic flux of the magnetostrictivematerial and changes the inductance of the coil 91. The change in theinductance varies the oscillating frequency of the LC oscillator circuit207. The varied oscillated frequency appears as a change in the countvalue, which is measured by the frequency measuring circuit 120 of thefixed circuit 100.

The controller 130 drives the motor 22 in accordance with the change inthe count value. The drive force of the motor 22 is transmitted to therear wheel 17 through the transmitting mechanism 3 to supplementmanpower.

In this embodiment, the variable impedance means comprises the core 90,which is a magnetostrictive material, and the coil 91, which is woundabout the core 90. Therefore, relative displacement between the crankaxle 40 and the drive gear 5 practically does not take place.Accordingly, pedaling is continued without the rider noticing anychanges.

Since there is substantially no mechanical displacement of the core 90,errors that would result from such displacement are small and the torqueapplied to the drive gear 5 is measured accurately.

Changes in the torque applied to the drive gear 5 are detected inaccordance with changes in the oscillating frequency of the LCoscillator circuit 207. Thus, even if the rotary coil 201 is moved byexternal force or displaced during assembly, the amplitude of the torquedetecting signal may change but its frequency will not change.Accordingly, mechanical errors of the rotary coil 201 will not affecttorque changes. This leads to accurate detection with high reliability.

This embodiment may employ a charging capacitor in the rectifying powersource circuit 204 of the rotated circuit 200 and stop the voltageON/OFF control, which is executed by the power source circuit 102 of thefixed circuit 100, for a predetermined period. During the stoppedperiod, electric discharge from the capacitor actuates the LC oscillatorcircuit 207. The oscillating frequency is measured by the frequencymeasuring circuit 120 by the amplifier 208 in the same manner asdescribed above.

In this case, the voltage waveform shown by α in FIG. 14(b) is inputinto the fixed coil 101. The frequency during stoppage of power supply(period A) is amplified by the amplifier 112 and measured by thefrequency measuring circuit 120.

Accordingly, the waveform obtained by superimposing the voltage waveformproduced through mutual induction of the rectangular waveform suppliedto the power source circuit 102 and the oscillating waveform generatedby the LC oscillator circuit 207 need not be filtered to extract onlythe oscillator voltage waveform. Furthermore, interference between thefrequency of the rectangular waveform voltage, which is supplied by thepower source circuit 102, and the frequency of the oscillating waveformgenerated by the LC oscillator circuit 207 becomes null. Accordingly,the frequency of the voltage waveform generated by the LC oscillatorcircuit 207 is detected accurately in the fixed circuit 100.

This embodiment employs the LC oscillator circuit 207 as a rotatedoscillator means. However, an astable multivibrator may be employedinstead. Furthermore, if a potentiometer is employed as the variableimpedance means, an RC oscillator circuit may be employed as the rotatedoscillator means.

In this embodiment, the rotated circuit 200 is actuated by the powersupplied by the fixed circuit 100. Alternatively, however, a battery maybe employed in the rotated circuit 100. In this case, the fixed circuit100 need not supply power to the rotated circuit 200. In this case, theswitching circuit 110 in the fixed circuit 100 and the rectifying powersource circuit 204 in the rotated circuit 200 become unnecessary.

THIRD EMBODIMENT

The rotated circuit 200 employed in this embodiment differs from thatemployed in the above embodiments. Parts similar to that employed in thefirst and second embodiments will not be described. In this embodiment,the structure of the fixed circuit 100 is the same as that of the secondembodiment.

As shown in FIG. 15, in the rotated circuit 200, a rotary coil 201 isconnected to a rectifying power source circuit 204, which includes arectifying/smoothing circuit 205 and a voltage stabilizing circuit 206.The rotated circuit 200 further includes a phase locked loop (PLL)circuit 210, which is supplied with electric power by the rectifyingpower source circuit 204, and an LC oscillator circuit 207.

In the same manner as the second embodiment, the drive gear 5 and thecrank axle 40 are connected to a core 90 (refer to FIG. 10), which ismade of a magnetostrictive material. A coil 91, which is connected tothe LC oscillator circuit 207, is wound about the core 90. Inductance ofthe core 90 and the coil 91 changes greatly when the power supplyvoltage is in the frequency bandwidth of 10² Hz to 10⁴ Hz, as shown inFIG. 16. However, changes in inductance may be detected as long as thepower supply voltage remains lower than about 10⁵ Hz.

As shown in FIG. 15, the LC oscillator circuit 207 is connected to thePLL circuit 210, which includes a phase comparator 211, a low-passfilter 212, a voltage control oscillator 213, and a divider 214.

The signal input to the PLL circuit 211 (signal that oscillates at 20kHz or higher and 100 kHz or lower) is converted to a control voltage bythe phase comparator 211. The voltage control oscillator 213 then raisesthe oscillating frequency to the MHz band. Next, the signal is dividedby the divider 214 at a dividing ratio of 1/100. The divided signal isthen fed back to the phase comparator 211 so that its phase is comparedwith the oscillating frequency of the LC oscillating circuit 207.

The phase comparator 211 generates a control voltage corresponding tothe phase difference between the two input signals. The low-pass filter212 then eliminates the high harmonic components from the controlvoltage. When the control voltage is input in the voltage controloscillator 213, the oscillating frequency is raised to the MHz band. Thesignal is then amplified by the amplifier 209 and superimposed on thevoltage waveform of the rotated circuit 200 and transmitted to the fixedcircuit 100 by the electromagnetic induction of the coils 201, 101.

In this embodiment, the frequency of the voltage waveform generated bythe LC oscillator circuit 207 of the rotated circuit 200, is raised froma bandwidth of 20 kHz or higher and 100 kHz or lower to the MHz band bythe PLL circuit 210. Thus, interference with the voltage waveform (20kHz), which is transmitted from the fixed circuit 100 to the rotatedcircuit 200 as a power source, does not occur. Accordingly, thefrequency of the voltage waveform generated by the LC oscillator circuit207, is accurately detected in the fixed circuit 100.

FOURTH EMBODIMENT

In the second and third embodiments, the LC oscillator circuit 207 isarranged in the rotated circuit 200, and the oscillating frequency ofthe LC oscillator circuit 207 is measured by the fixed circuit 100 inorder to measure the torque applied to the drive gear 5.

In a fourth embodiment, as shown in FIG. 17, an LC oscillator circuit113, which serves as a fixed oscillating means, is arranged in the fixedcircuit 100. The inductance at the side of the fixed coil 101 is variedin accordance with the torque applied to the drive gear 5. In thisstate, the oscillating frequency of the LC oscillator circuit 113 ismeasured to obtain the torque applied to the drive gear 5.

The frequency measuring circuit 120 employed in this embodiment is thesame as that employed in the second embodiment.

In the same manner as the second embodiment shown in FIG. 10, the drivegear 5 and the crank axle 40 are connected to each other by a core 90,which is made of a cylindrical magnetostrictive material. As shown inFIG. 17, the rotated circuit 200 includes the core 90, which serves as avariable impedance means and is made of a magnetostrictive material, thecoil 91, and the rotary coil 201, which is connected to the coil 91.

The fixed circuit 100 includes a fixed coil 101, which is arranged nearthe rotary coil 201, the LC oscillator circuit 113 for varying theoscillating frequency in accordance with the inductance of the fixedcoil 101, the frequency measuring circuit 120 for measuring theoscillating frequency of the signals oscillated by the LC oscillatorcircuit 113, a controller 130 for controlling the drive force of themotor 22 in accordance with the measuring results of the frequencymeasuring circuit 120, and a direct current power source 103.

The LC oscillator circuit 113 generates a sine wave that varies withinan oscillating frequency of about 4.4 kHz to 4.7 kHz in accordance withchanges in the inductance of the fixed coil 101. In this state, theinductance of the fixed coil 101 is determined by its self-inductance,the inductance of the rotary coil 201, and the inductance of the coil91.

A great load is applied to the drive gear 5 when starting to move thebicycle 1, accelerating the bicycle 1, or climbing slopes with thebicycle 1. The load applies a compressing force to the core 90, which ismade of a magnetostrictive material and located between the crank axle40 and the drive gear 5. This alters the magnetic field of the core 90and varies the inductance of the coil 91. As a result, the inductance ofthe fixed coil 101 is varied. Accordingly, the varied inductance of thefixed coil 101, which is connected to the LC oscillator circuit 113,changes the oscillating frequency of the LC oscillator circuit 113.

The oscillating voltage waveform generated by the LC oscillator circuit113 is input to the frequency measuring circuit 120. The frequencymeasuring circuit 120 counts the cycle of the edge pulses generated bythe oscillating voltage waveform and inputs the count value to thecontroller 130.

The controller 130 controls the drive force of the motor 22 based on theoscillating frequency of the LC oscillator circuit 113, which is storedin an incorporated memory (not shown), and the torque applied to thedrive gear 5. The drive force is then transmitted to the rear wheel 17by means of the transmitting mechanism 3 to supplement manpower.

In this embodiment, the LC oscillator circuit 113, which serves as afixed oscillating means, is provided in the fixed circuit 100 to detectchanges in the torque applied to the drive gear 5 caused by changes inthe frequency of the LC oscillator circuit 113. Accordingly, power neednot be supplied to the rotated circuit 200. This simplifies thestructure of the rotated circuit 200.

FIFTH EMBODIMENT

In this embodiment, the cylindrical core 90, which is made of amagnetostrictive material, is supported in a different manner from theabove embodiments. The core 90 is arranged in the space between thedrive gear 5 and the crank arm 61.

As shown in FIGS. 18 and 19, a coupling member 256, from which areceiving plate 258 projects toward the crank arm 61, is fixed to twoadjacent ribs 52 of the drive gear 5. A rod-like coupling member 266,from which a pressing piece 268 projects facing the receiving plate 258in the rotating direction, is inserted through a bore of the crank arm61 and thus fixed.

The core 90 has a second end surface 93, which is coupled with and fixedto the receiving plate 258, and a first end surface 93, which is coupledwith the pressing piece 268. A coil 91, which is the same as thatemployed in the second to fourth embodiments, is wound about theperipheral surface of the core 90. The electric circuit structure is thesame as that employed in the fourth embodiment.

In this embodiment, the core 90 is arranged in the space between thedrive gear 5 and the crank arm 61. Thus, the core 90 is encompassed bythe drive gear 5 and the crank arm 61. Accordingly, the rider's feet,flying pebbles, or the like, do not hit and/or damage the core 90.

Since the pressing piece 268 is coupled to the crank arm 61, a supportplate 166, such as that employed in the second embodiment and shown inFIG. 10, need not be employed.

In this embodiment, the core 90 is arranged in the space between thedrive gear 5 and the crank arm 61. However, the rotated circuit 200 mayfurther be arranged in the space between the drive gear 5 and the crankarm 61.

Furthermore, in this embodiment, the pressing piece 268 and thereceiving plate 258 and the associated end surfaces 92, 93 of the core90 are directly connected to each other. However, an elastic plate madeof rubber or the like may be arranged between the pressing piece 268 andthe first end surface 92 of the core 90 or between the receiving plate258 and the second end surface 93 of the core 90. This would obtain thedesirable parallelism between the pressing surface of the pressing piece268 and the first end surface 92 of the core 90 or between the receivingsurface of the receiving plate 258 and the second end surface 93 of thecore 90.

SIXTH EMBODIMENT

In this embodiment, a further pressing mode of the core 90, which ismade of a magnetostrictive material, is employed. Parts that areidentical to that employed in the fifth embodiment will not bedescribed.

Referring to FIG. 20, the core 90 is located in a cuplike container 97,which is a magnetic body, with a coil 91 wound thereabout. The coil 91is surrounded by the walls of the container 97. The core 90 has a firstend surface 92 facing an opening of the container 97. A second endsurface 93 faces the bottom inner surface of the container 97 and isthus covered by the surface.

A rubber plate 94, which serves as an elastic plate, is arranged betweenthe second end surface 93 of the core 90 and the bottom inner surface ofthe container 97. A metal plate 96, which serves as a plate member, isattached to the first end surface 92 with a rubber plate 95, whichserves as an elastic plate, arranged in between. The shape and dimensionof the rubber plates 94, 95 and the metal plate 96 are substantially thesame as the end surfaces 92, 93 of the core 90.

The bottom outer surface of the container 97 is fixed to the receivingplate 258 on the coupling member 256 of the drive gear 5 and arrangedsuch that the metal plate 96 abuts against a round pressing surface 269of the pressing piece 268.

In this structure, when force is applied to the crank arm 61, the roundpressing surface 269 causes the pressing piece 268 to apply force on themetal plate 96 at a single point. Thus, a uniform force is applied tothe entire first end surface 92 of the core 90 by way of the rubberplate 95. This prevents erroneous detection caused by biased abutmentand local fatigue or damage of the core 90.

The rubber plate 94 arranged between the receiving plate 258 and thecore 90 prevents biased abutment between the receiving plate 258 and thecore 90. The core 90 and the container 97, which accommodates thereceiving plate 258, are made of magnetic bodies. Thus, leakage fluxfrom the core 91 is decreased. This improves detecting sensitivity.

In this embodiment, the pressing surface 269 of the pressing piece 268is round. However, the receiving plate 258 can be provided with a roundpressure receiving surface with the pressing piece 268 having a flatpressing surface 269. In this case, the bottom outer surface of thecontainer 97 is fixed to the pressing piece 268 on the coupling memberof the drive gear 5 and arranged such that the metal plate 96 abutsagainst the round abutting surface of the receiving plate 258.

In this embodiment, the rubber plates 94, 95 are employed as elasticplates. However, the material of the elastic plates is not limited torubber. Materials having elasticity such as synthetic resin may beemployed instead as the elastic plates.

In this embodiment, the metal plate 96 is employed as the plate member.However, the material of the plate member need not be limited to metalas long as the plate member does not deform greatly and break due to theforce applied to the pressing piece 268 or the receiving plate 258 whenthe pedals 62 are turned. Furthermore, if the plate member is magnetic,the plate member and the container 97 eliminate leakage flux from thecoil 91 and improve detection sensitivity.

SEVENTH EMBODIMENT

In this embodiment, a further mode for the installation of the rotarycoil 201 and the fixed coil 101 is employed.

As shown in FIG. 21, an annular cap 48, which serves as a support plate,is coupled to the crank axle 40 at the right side of the bottom bracket15 with a coil spring 78, which serves as an urging means, arrangedbetween the crank axle 40 and the cup 48. The annular cap 48 is movablein the axial direction of the crank axle 40. Furthermore, the cap 48 issupported by the bottom bracket 15 by a coupling means, such as abracket (not shown), so that the cap 48 remains fixed at a certainposition even if the crank axle 40 is rotated. One end of the coilspring 78 is fixed to the bottom bracket 15, while the other end isfixed to the left surface of the cap 48 to prevent the coil spring 78from following the rotation of the drive gear 5. Accordingly, the urgingforce of the coil spring 78 constantly urges the cap 48 toward the drivegear 5.

A bearing race 49 a and a ring core 42 having a U-shaped cross-sectionare coaxially fixed to the right surface of the cap 48. The ring core 42has a U-shaped cross-section with an opening facing the drive gear 5.The fixed coil 101 is wound in the opening along the rotating directionof the drive gear 5.

A case 44 is fixed to the left surface of the drive gear 5. The case 44includes a donut-like bottom portion 47, an annular outer wall portion45, which projects toward the cap 48 along the periphery of the bottomportion 47, and an annular inner wall portion 46, which projects towardthe cap 48 at a location inward from the outer wall portion 45.

A bearing race 49 b is fixed to the inner side of the inner wall portion46. A plurality of balls 49 c are held between the two bearing races 49a, 49 b. The bearing races 49 a, 49 b and the balls 49 c form a thrustbearing 49, which serves as a spacer and a ball bearing. A ring core 43having a U-shaped cross-section is fixed to the bottom portion 47 facingthe ring core 42, which is fixed to the cap 48. The ring core 43 has anopening in which the rotary coil 201 is wound along the rotatingdirection of the drive gear 5.

In this embodiment, the cap 48, in which the fixed coil 101 is arranged,is constantly urged toward the rotary coil 201. This maintains aconstant distance between the fixed coil 101 and the rotary coil 201regardless of swinging or vibrations. Accordingly, the reliability andmeasuring accuracy of the measured torque signals is enhanced.

In this embodiment, the thrust bearing 49 is arranged between the cap48, which holds the fixed coil 101, and the case 44, which holds therotary coil 201. Thus, the rotary coil 201, which is arranged in thecase 44, keeps rotating smoothly regardless of the cap 48 being urgedtoward the drive gear 5 by the coil spring 78.

Furthermore, the expansion and contraction of the coil spring 78 and theexistence of the thrust bearing 49 maintain a constant distance betweenthe fixed coil 42 and the rotary coil 43 even if the length of the crankaxle 40 projecting from the bottom bracket 15 differs due to dimensionaldifferences that occur during production or due to application to adifferent type of bicycle. Accordingly, the structure related to thecoils 42, 43 need not be designed for each bicycle type to keep aconstant distance between the coils 42, 43. Furthermore, burdensomeprocesses such as fine adjustment of the distance between the coils 42,43 need not be performed.

Additionally, this embodiment prevents the infiltration of mud and dustinto the case 44.

In this embodiment, the coil spring 78 is employed as the urging means.However, a leaf spring, rubber, or the like may be employed as theurging means.

In this embodiment, the thrust bearing 49 is employed as the spacer andthe ball bearing. However, as shown in FIG. 22, a radial bearing 149 maybe employed instead. In this case, a bearing race 149 a is fixed to thecap 48, a bearing race 149 b is fixed to the inner side of the innerwall portion 46 of the case 44, and balls 149 c are held between the tworaces 149 a, 149 b in the same manner as the thrust bearing 49.

In this embodiment, the bearing race 49 b and the ring core 43 may bedirectly coupled with the drive gear 5.

In the first to seventh embodiments, the present invention is applied toa two wheel bicycle, which drive wheel is the rear wheel 17. However,the present invention may be applied to a front wheel drive bicycle orother types of manpowered vehicles.

In the first to seventh embodiments, the torque applied in the rotatingdirection of the drive gear 5 and the crank axle 40 is detected.However, the torque applied in the rotating direction of the driven gear73 and the axle 72 may be detected.

In the first to seventh embodiments, the rear wheel 17, which is thedrive wheel, is driven by the drive force produced by manpower and thedrive force produced by an auxiliary power apparatus. However, the driveforce produced by manpower and the drive force produced by an auxiliarypower apparatus may be supplied to two different wheels. For example, ina two wheel bicycle, the rear wheel may be the manpower drive wheel andthe front wheel may be the power apparatus drive wheel.

What is claimed is:
 1. A manpowered vehicle equipped with an auxiliarypower apparatus having a power source for supplementing the driving ofthe vehicle, comprising: a main body; a rotated body supported by themain body and driven by manpower, wherein the rotated body includes, acrank axle pivotally supported by the main body, a drive gear rotatablycoupled to the crank axle, and a crank arm having a basal end attachedto the crank axle and a distal end on which a pedal is arranged torotate the crank arm integrally with the crank axle, wherein the drivegear is connected to a manpowered drive wheel; a rotary coil arrangedcoaxially with the rotated body; a variable impedance means electricallyconnected to the rotary coil and having an impedance that varies withthe load applied to the rotated body, wherein the variable impedancemeans includes a core made of a magnetostrictive material and a coilarranged on one part of an outer surface of the core, wherein aremaining part of the outer surface of the core is supported between thecrank axle and the drive gear, and the impedance of the coil varies bydeformation of the core that corresponds to the load acting on the drivegear; a fixed coil fixed to the main body such that the fixed coil isconcentric with and spaced by a predetermined distance from the rotarycoil, wherein the fixed coil is electromagnetically coupled with therotary coil; a detector, connected with the fixed coil, that detectschanges in electric current or voltage of the fixed coil caused by therotary coil in accordance with the impedance varied by the variableimpedance means, and generating a corresponding output value; and acontrol means for controlling the power source based on the output valueof the detecting means.
 2. The manpowered vehicle of claim 1, furthercomprising: a power source circuit for supplying electric power in acyclic manner to the fixed coil, wherein the supply of electric powergenerates induced electromotive force in the rotary coil.
 3. Themanpowered vehicle according to claim 2, wherein the auxiliary powerapparatus operates by using the induced electromotive force generated bythe rotary coil as an electric power source.
 4. The manpowered vehicleof claim 3, wherein the oscillating means is connected to the rotarycoil and the frequency of signals supplied to the fixed coil by theoscillating means via the rotary coil differs from the frequency of theelectric power supplied to the rotary coil by the power source circuitvia the fixed coil.
 5. The manpowered vehicle of claim 3, wherein thetiming of signals supplied to the fixed coil by the oscillating meansvia the rotary coil differs from the timing of the electric powersupplied to the rotary coil by the power source circuit via the fixedcoil.
 6. The manpowered vehicle according to claim 1, wherein the crankarm includes a pressing piece that projects toward the drive gear, andthe drive gear includes a receiving piece facing the pressing piecealong the rotating direction; and the core is arranged between thepressing piece and the receiving piece.
 7. The manpowered vehicleaccording to claim 1, wherein the detector measures an amplitude of theelectric current flowing through the fixed coil or the intensity of thevoltage.
 8. The manpowered vehicle according to claim 1, wherein theauxiliary power apparatus includes an oscillating means that varies theoscillating frequency in accordance with the impedance varied by thevariable impedance means.
 9. The manpowered vehicle according to claim8, wherein the oscillating means is connected to one of the fixed coiland the rotory coil.
 10. A manpowered vehicle equipped with an auxiliarypower apparatus having a power source for supplementing driving of thevehicle, comprising: a main body; a rotated body supported by the mainbody; a rotary coil arranged coaxially with the rotated body; a variableimpedance electrically connected to the rotary coil and having animpedance that varies with the load applied to the rotated body, thevariable impedance including a core made of a magnetostrictive materialand a coil arranged on one part of an outer surface of the core, whereinthe remaining part of the outer surface of the core is supported betweenthe crank axle and the drive gear, and the impedance of the coil isvaried by deformation of the core that corresponds to the load acting onthe drive gear; a fixed coil attached to the main body such that thefixed coil is concentric with and spaced from the rotary coil, whereinthe fixed coil is electromagnetically coupled with the rotary coil; adetector, connected with the fixed coil, that detects changes in atleast one of electric current and voltage of the fixed coil caused bythe rotary coil in accordance with the impedance varied by the variableimpedance and generating a corresponding output value; and a controlmeans for controlling the power source based on the output value of thedetecting means.
 11. The manpowered vehicle according to claim 10,wherein the crank arm includes a pressing piece that projects toward thedrive gear, and the drive gear includes a receiving piece facing thepressing piece along the rotating direction, and wherein the core isarranged between the pressing piece and the receiving piece.
 12. Amanpowered vehicle equipped with an auxiliary power apparatus having apower source for supplementing the driving of the vehicle, comprising: amain body; a crank axle pivotally supported by the main body; a drivegear rotatable coupled to the crank axle; a crank arm attached to thecrank axle, wherein a load exerted on the crank arm by manpower is usedto rotate the crank axle and the drive gear; a pressing piece attachedto the crank arm and projecting towards the drive gear; a receivingpiece attached to the drive gear and facing the pressing piece; a rotarycoil arranged coaxially with the rotated body; a variable impedanceelectrically connected to the rotary coil and having an impedance thatvaries with the load applied to the rotated body, the variable impedanceincluding a core made of a magnetostrictive material and a core coilarranged on an outer surface of the core, wherein the core is arrangedbetween the pressing piece and the receiving piece and the impedance ofthe core coil is varied by deformation of the core that corresponds tothe load acting on the drive gear; a fixed coil attached to the mainbody such that the fixed coil is concentric with and spaced by apredetermined distance from the rotary coil, wherein the fixed coil iselectromagnetically coupled with the rotary coil; a detector, connectedwith the fixed coil, that detects changes in electrical current orvoltage of the fixed coil caused by the rotary coil in accordance withthe impedance varied by the variable impedance, and generating acorresponding output value; and a controller for controlling the powersource based on the output value of the detecting means.